Milk & Meat in Our Diet: Good or Bad for Health & Wealth?

Professor Ian Givens of the University of Reading outlined the evidence concerning the health benefits (and otherwise) of animal products in the human diet in the 21st century at this year's meeting of the British Society of Animal Science. Jackie Linden summarises his main points for ThePoultrySite.

Professor Ian Givens
University of Reading

Introduction

Although globally the demand for animal-derived foods is growing rapidly, driven by a combination of population growth, urbanisation and rising income, the contribution of milk and red meat in the UK diet has reduced considerably over the last 50 years, said Professor Givens. The contribution of poultry meat, however has increased enormously. Mainly because of their major contribution to saturated fatty acid (SFA) consumption, ruminant-derived foods have often been considered to be a major contributor to coronary heart disease (CHD) and cardiovascular disease (CVD) and other chronic disorders.

Given that we are living in an era of increasing risk of chronic disease as a result of increased obesity and an ever-ageing population, it is important that risks and benefits associated with different foods and understood and that possible improvements to such foods are made with regard to the cost-effectiveness and environmental impact, Professor Givens warned.

Epidemiological Evidence

He explained that a recent meta-analysis of 15 studies showed the relative risk of stroke and/or heart disease in subjects with high milk and dairy consumption was 0.84 (95 per cent confidence interval 0.76, 0.93) and 0.79 (0.75,0.82), respectively, relative to the risk in those with low consumption.

Four studies reported incident diabetes as an outcome, and the relative risk in the subjects with the highest intake of milk and dairy foods was 0.92 (0.86, 0.97).

Thus, set against the proportion of total deaths attributable to life-threatening diseases in the UK – vascular diseases, diabetes and cancer – Professor Givens said the results of the meta-analysis provide evidence of an overall survival advantage from the consumption of milk. The situation with other dairy foods is less clear.

A positive association between increased milk consumption and prostate cancer has been seen, however, and should not be ignored.

Similarly, confirmation by the World Cancer Research Fund/American Institute for Cancer Research (WCRF/AICR) of an increased risk of colo-rectal cancer in consumers of red meat and processed meat needs attention, not least to assess the relative risks associated with different so called 'red meats', he said.

Saturated Fatty Acids

Professor Givens said that despite the recognised benefits of limiting SFA intake in the UK, men and women currently exceed the current mean population target for SFA intake (less than 11 per cent of total food energy) by 22 and 20 per cent, respectively. The proportion of UK children exceeding the target is even greater.

Manipulating the fat composition of ruminant-derived foods holds considerable potential as a means of reducing SFA intake and providing health benefits, he explained. Use of cis-mono unsaturated fatty acid (MUFA)-rich oils in the diet of the cow can reduce SFA in milk fat typically from 70 per cent to 55 to 60 per cent of total fatty acids, whilst increasing cis-MUFA from typically 20 per cent to 33 per cent of total fatty acids. If applied to all UK milk, this would reduce SFA entry into the food chain by some 90,000 tonnes per year, and would provide additional benefits to the environment through reduction of methane produced by dairy cows.

The health benefits of this SFA replacement strategy is supported by impact modelling and by human intervention studies, although more of the latter are urgently needed with more functional outcomes being assessed, Professor Givens said.

Omega-3 Fatty Acids

The beneficial effects of long-chain (LC; carbon chain 20 or more) n-3 polyunsaturated fatty acids (PUFA) are well documented. However, recent evidence indicates that few people achieve the daily recommended intake for adults of 450 mg of EPA (eicosapentaenoic acid) + DHA (docosahexaenoic acid) per day.

In many parts of Europe, the daily intake of EPA + DHA by adults – and especially young people – is less than 100 mg per day, since many never eat oily fish. Poultry meat contributes small but worthwhile amounts of EPA + DHA, and Professor Givens showed an example of studies to enrich the EPA + DHA content and how it could impact intake.

There is also considerable concern that intake of n-6 PUFA has increased excessively over the last 40 years and is aggravating the effects of low LC n-3 intake, Professor Givens said. Animal-derived foods share some of this responsibility for the increased consumption of n-6 fatty acids and he stressed the particular role of poultry meat products. Substantial changes in the use of oils in the food chain will be needed to deal with this issue, he said.

Cost-Benefit

Currently, CVD alone is estimated to cost the European Union € 170 to 190 billion per annum, and is likely to rise due to an ageing population, according to Professor Givens. A recent cost-benefit analysis in the Lipogene project of reducing SFA intake through dairy cow nutrition indicates that a positive outcome via reduced health care costs would be reached within five years. Thus the economic scope for some dietary change would appear to large but more complex models are needed.

Conclusions

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"A major political challenge will be the redirection of health care savings back to support changes in primary food production"

Professor Givens summarised the findings, saying that milk appears to offer some protection to the cardiovascular system and overall, it provides a slight advantage in terms of survival. Reducing the SFA in milk fat would provide further benefits.

Red meat is associated with increased relative risk of colo-rectal cancer but intake is falling and so this needs to be seen in context. He contrasted this with poultry meat, saying "Poultry meat and products are diverse foods and since they are eaten in large amounts, there needs to be more concern over its lipid content and composition, especially for children".

He concluded that animal-derived foods have a key role in the diet but they have some negative issues. "These should be seen in context but not ignored," Professor Givens advised the audience.

Inputs into the animals' diet can have a major impact on the overall healthiness of foods, and Professor Givens urged the food industry to take greater responsibility for this than they have done hitherto. Providing incentives would provide some financial benefits, he suggested, but the economics of other changes needs further work.

There needs to be much greater join-up across the food chain over research activity and funding at all levels of food supply, he added.

"Ultimately, the direction of any population-directed diet modification will depend on the cost-benefit analysis and political will. A major political challenge will be the redirection of health care savings back to support changes in primary food production," Professor Givens concluded.